Forming a relief by developing and hardening an exposed unhardened silver halide emulsion in the exposed areas with 3-pyrazolidones having hydroxymethyl substitution in the 4-position



United States Patent US. Cl. 96-36 14 Claims ABSTRACT OF THE DISCLOSURE A relief image can be formed by developing an exposed unhardened photographic silver halide emulsion with a composition containing a compound of the formula:

CHrOH CH2 NH wherein R is hydrogen or a lower alkyl group, such as hydroxymethyl, hydroxyethyl, hydroxypropyl, methyl, ethyl, propyl and the like; and R is aryl, such as phenyl, methyl phenyl, aminophenyl and the like. Unhardened photographic emulsions and photographic elements containing such 3-pyrazolidone compounds are especially useful.

This invention relates to novel tannning developers which will cause imagewise hardening of an unhardened silver halide emulsion during development. A relief image can then be formed by removing the unhardened emuls1on.

When a gelatin-silver halide emulsion is developed in a tanning developer, cross-links are formed between the long-chain gelatin molecules by the products of oxidat-ion of the developing agent, thereby causing the gelatin to become hardened and highly insoluble. Well-known developing agents that are able to tan gelatin have at least two functional hydroxyl groups such as catechol, pyrogallol, hydroquinone and certain derivatives of these compounds. Compounds with only one functional hydroxyl group such as p-aminophenol, monomethyl-p-aminophenol (Metol), and diaminophenol '(Am-idol), along with compounds such as the p-phenylenediamines exhibit very little or no tanning action. The well-known tanning agents act to produce quinones which cause the localized hardening of the gelatin. In this invention, the oxidized developing agent acts to release an aldehyde which accomplishes an imagewise hardening of the gelatin.

It is an object of this invention to provide a method of forming a relief image in an unhardened emulsion by using a novel tanning developer.

Another object is to provide a process for developing an exposed, unhardened silver halide emulsion with a novel developer.

A further object is to extend tanning development to a new class of developing agents which offer an improved speed-contrast relationship.

Still another object is to provide a tanning development method wherein the staining propensities of conventional quinone-producing developing agents 'are avoided.

A further object is to provide a tanning development method wherein. antioxidants may be incorporated into the developer.

Patented July 1, 1969 Still another object is to provide silver halide photographic elements having an improved tanning developing agent incorporated therein.

Still further objects will become apparent from the following specification and claims.

According to my invention, it has been found that a relief image may be formed by developing an exposed, unhardened silver halide emulsion with a composition containing a compound having the following formula:

. in which R is hydrogen or a lower alkyl group (including substituted lower alkyl groups) and R is an aryl group (including substituted aryl groups). This development step will cause an image of hardened silver halide emulsion to be for-med in the exposed area i.e., the process comprises imagewise hardening and developing an exposed unhardened silver halide emulsion with the described composition. When the unexposed unhardened silver halide emulsion is removed as by washing in hot water, for example, a relief image is formed.

Included within the definition of R in the above formula are hydroxyalkyls such as hydroxymethyl, hydroxyethyl, hydroxypropyl, etc; lower alkyls such as those containing 14 carbon atoms; and groups such as methyl, ethyl, propyl, and butyl substituted with carboxy or sulfo groups. Included within the definition of R in the above formula are phenyl and phenyl substituted with groups such as methyl, chloro, amino, methylamino, acetylamino, methoxy, and methylsulphonoamidoethyl. especially preferred compounds falling within the above formula are 1-phenyl-4,4-dihydroxymethyl-3-pyrazolidone and 1-phenyl-4-methyl-4-hydroxymethyl-3-pyr-azolidone.

According to my invention, an unhardened silver halide emulsion is one which has a melting point of less than about F. The melting point is determined by immersing a coated support in water which is heated at the rate of 6 F. per minute with brushing of the emulsion surface with a soft bristle brush. The temperature at which there is evidence of emulsion removal is taken as the melting point.

Various 3-pyrazolidones are known in the prior art. For example, US. Patent 2,772,282 of Allen et al., granted Nov. 27, 1956, describes various 4,4-dialkyl-3- pyrazolidones. These developers are used on conventional hardened silver halide emulsions however, and do not have any hydroxymethyl groups in the 4-position for imagewise release of a formaldehyde. US. Patent 3,221,023 of De Marle et al., granted Nov. 30, 1965, discloses 3- pyrazolidones which may have hydroxymethyl groups in the 4-position, but these compounds are also substituted in the 2-position and are not disclosed as being useful to develop an unhardened silver halide emulsion.

The ability of l-phenyl-3-pyrazolidone developing agents to produce high emulsion speed at low contrast is well known. Heretofore, however, such agents could not be used for tanning development. The developing agents of this invention make use of this advantage. On the other hand, well-known tanning developers such as catechol and hydroquinone give low speed unless development is to high contrast.

This invention also avoids the staining propensity of the well-known tanning agents which produce quinones to cause the localized hardening of the gelatin. These quinones cause highly colored stain on film, paper, hands, equipment, etc. This stain is avoided by use of the com pounds described in this invention. Instead of quinones being produced during development, the developing agents of this invention produce an aldehyde which accomplishes the imagewise hardening of the gelatin.

An additional advantage of this invention is that it permits the incorporation of antioxidants in the developer. Conventional antioxidants such as sulfite and ascorbic acid react with quinone to remove the quinone from solution and prevent its tanning action on the gelatin. The aldehyde which is produced by the compound of this invention does not react to any appreciable degree with ascorbic acid and only to a limited extent with sodium sulfite, especially at high pH value. Thus, these antioxidants may be incorporated into the developer to protect it from aerial oxidation.

A gelatin relief image produced by the process of this invention by virtue of the density provided by the developed silver comprises a useable photographic image. In addition, the difference in absorption between the gelatin relief areas and the background can be used for imbibition of dye solutions for transfer to mordanted receiving sheets. The relief can also be used in photomechanical processes, such as typography or gravure. The relief can be transferred to other supports, such as silk screen for stencil printing and the like. Alternatively, the difference in the ink receptivity of the reacted and unreacted areas can be employed directly without wash-off as in the lithographic printing process of US. Patent 3,146,104, issued Aug. 25, 1964, to Yackel et al. The developers of the invention may also be used in colloid transfer systems such as that of US. Patent 2,596,752, issued May 13, 1952.

The developing agents of this invention can be used in emulsions intended for use in dilfusion transfer processes which utilize the undeveloped silver halide in the nonimage areas of the negative to form a positive by dissolving the undeveloped silver halide and precipitating it on a receiving layer in close proximity to the original silver halide emulsion layer. Such processes were first described in Rott US. Patent 2,352,014, issued June 20, 1944. By using the developing agents of my invention in a diffusion transfer process, a hardened positive image may be formed in an unhardened receiving layer.

My novel tanning developing agents are also valuable for use in the porous layer of processing elements used to carry the photographic developing chemicals for web processing. Such processing elements and web processes using these elements are described in the Tregillus et al. U.S. Patent 3,179,517, issued Apr. 20, 1965.

The following examples will illustrate the invention but are not to be construed to limit it in any way.

EXAMPLE 1 A piece of Kodak Matrix film, which is an unhardened silver halide emulsion coated on a film support, was exposed and processed for ten minutes in the following solution (pH=ll.5) maintained at 25 C.:

Grams 1-phenyl-4,4-dihydroxymethyl-3-pyrazolidone 0.44 Sodium sulfite, anhydrous 2.0 Sodium carbonate, anhydrous 20.0

Water to make 1 liter.

After development, the film was placed in a 5% acetic acid solution and then immersed in warm water at about 36 C. The unhardened gelatin and the unexposed silver' 4 EXAMPLE 2 A piece of film as in Example 1 was exposed and processed at 25 C. in the following solution (pH=ll.5):

Sodium carbonate (anhydrous) 20.0 Water to make 1 liter.

After a five-minute development, the film was placed in a 5% acetic acid solution and then placed in warm Water at 37 C. causing the unhardened gelatin in the unexposed areas to be washed off. However, the gelatin area where exposure had taken place remained firmly attached to the support. The temperature of the Water was raised to 50 C. without affecting the hardened gelatin area. Not until the temperature of the water reached 82 C. was there any significant removal of the image area. In addition, the density of the developed image was 0.5 higher than in Example 1.

EXAMPLE 3 A control sample was developed in a solution similar to that of Example 2 above using the same procedure except that the developer solution contained l-phenyl- 3-pyrazolidone instead of 1-phenyl-4,4-dihydroxymethyl- 3-pyrazolidone. After development, the film was placed in a 5% acetic acid solution and then placed for five minutes in a fixing bath which did not contain any hardener. The sample was then immersed in warm water at 35 C. The entire image area was removed as well as the unexposed area.

This comparison clearly shows the effectiveness of the substituted derivative in Example 2 above in forming a relief image as compared to the unsubstituted compound of Example 3 which forms no relief image.

EXAMPLE 4 The procedure of Example 2 was repeated using 1- phenyl-4-methyl-4-hydroxymethyl-3-pyrazolidone instead of 1-phenyl-4,4-dihydroxymethyl-3-pyrazolidone. Development was carried out for 5, 10 and 20 minutes with the following results:

Melting range Developing time of gelatin in (minutes) Imago denslty Fog density image area (O.)

It is seen from this example that increased development times harden the gelatin to a greater extent.

The novel 4-substituted 3 pyrazolidone developing agents of this invention can be used to advantage in developer compositions used for developing any photographic emulsion layers containing silver halide such as silver chloride, silver bromide, silver iodide, silver chlorobromide, silver bromoiodide, silver chlorobromoiodide, etc. The developer composition may contain the 4-substituted-3-pyrazolidone compound as the sole developing agent or may contain this developing agent in combination with other developing agents to give superadditive effects or to give other desired effects. Other developing agents which are commonly used with the developing agents of this invention include the following: hydroquinone; substituted hydroquinones; resorcinol; catechol; ascorbic acid; gallic acid; the aminophenols, such as p-methylaminophenol sulfate, the phenylenediamines, etc.

The concentration of auxiliary developing agents can be varied and, of course, no auxiliary developing agent need be employed unless so desired. Useful concentrations of auxiliary developing agents vary from about 0.01 mole to 2.0 moles per mole of developing agent. De-

pending upon the particular auxiliary developing agent employed, larger or smaller quantities can be used.

In addition to the developing agent or agents, my developer usually contains an alkali such as sodium carbonate, potassium carbonate, trisodium phosphate, sodium pyroborate, sodium metaborate, sodium hydroxide, potassium hydroxide, etc. My composition may contain a preservative such as an alkali sulfite, for example, sodium sulfite, potassium sulfite, etc., an alkali bisulfite, such as sodium bisulfite, potassium bisulfite, etc., an alkali metabisulfite, such as sodium metabisulfite, potassium metabisulfite, etc. Other material may be added to my developer composition such as the sequestering agents of Henn U.S. Patent 2,625,476, issued J an. 13, 1952, and Henn et al. U.S. Patent 2,656,273, issued Oct. 20, 1953; the stabilizers of Haist et a1. U.S. Patent 2,875,048, issued Feb. 24, 1959; antifoggants such as benzotriazole; development restrainers such as the alkali bromides, iodides, etc. 7

Other addenda known in the art may be employed with the silver halide emulsions used in my invention. The silver halide emulsions may be chemically sensitized with compounds of the sulfur group, e.g., sulfur sensitizers, selenium sensitizers, tellurium sensitizers, noble metal salts, such as gold or reduction sensitizers with reducing agents or combinations of such sensitizers. The silver halide emulsions of this invention may contain spectral sensitizers, such as the cyanines, merocy'anines, styryls, hernicyanines, speed-increasing compounds such as polyalkylene glycols, onium salts and thioethers, stabilizers such as azaindenes, cadmium and other divalent salts, mercury compounds, azoles and mercaptans, coating aids, such as nonionic, anionic and amphoteric surface active agents, etc.

The addenda which have been described may be used in various kinds of photographic emulsions. In addition to being useful in X-ray and other nonoptically sensitized emulsions, they may also be used in orthochromatic, panchromatic, infrared sensitive emulsions, and lith type emulsions which usually are developed to high contrast in developing solutions having a low concentration of sulfite ions. They may be added to the emulsion before or after any sensitizing dyes which are used. The agents may be used in emulsions intended for color photography, for example, emulsions containing color-forming couplers or emulsions to be developed by solutions containing couplers or other color-generating materials, emulsions of the mixed-packet type, such as described in Godowsky U.S. Patent 2,698,794, issued Jan. 9, 1955; or emulsions of the mixed-grain type, such as described in Carroll and Hanson U.S. Patent 2,592,243.

My novel tanning developing agents may be incorporated directly into an unhardened silver halide emulsion layer on a support or in a layer, such as a gelatin layer, contiguous to the silver halide emulsion layer. Development would then occur by activating the developer with an aqueous solution of an alkaline material such as sodium carbonate, sodium hydroxide, potassium carbonate, potassium hydroxide, etc. Other elements may have alkaline material incorporated in them so that development may be accomplished simply by applying water or by heating the element so as to make available for development moisture that is already in the element.-

The concentration of the developing agents used in my invention will vary depending upon the particular chemical compound involved and the location of the compound within the photographic element. That is, if the tanning agent is incorporated within the silver halide emulsion undergoing development, it may be desirable to use a somewhat different concentration than would be used if the developer were incorporated in a layer contiguous to the photographic silver halide emulsion. The useful concentration of developer for incorporation in the emulsion is from about 0.01 to about 4.0 moles/mole of silver halide. For incorporation in a layer contiguous to the silver halide emulsion layer, somewhat larger concentrations of developer can be tolerated without adverse effects. When the developer is used in an aqueous developer composition, any quantity may be used which will reduce the silver halide in the emulsion to silver. Especially good results are obtained when the compound is present in the developer composition in an amount ranging from about 0.2 to about 4 grams per liter.

While the tanning developers of this invention are particularly described with reference to tanning gelatin, they may also be used to tan other colloids such as albumin, polyvinyl alcohol, agar-agar, sodium alginate, hydroxylated cellulose esters, hydrophilic polyvinyl copolyesters, etc.

The supports which may be used for the silver halide emulsions referred to herein are those customarily used, such as paper, glass, metal, wood, cloth, polymeric materials such as polyolefins, polyesters, cellulose esters, polyamides, polystyrene, polycarbonates, etc. A particularly useful support is paper coated with a polyolefin such as polyethylene.

The formaldehyde which is produced by the developing agents of my invention may be advantageously employed for other desired ends than the hardening of gelatin in the areas of image development. For example, it may take part in a coupling or color-forming reaction similar to that disclosed in U.S. Patent 2,805,158. The formaldehyde so produced might also act catalytically to promote imagewise diiferentiation of other properties of the developed layer as a function of the developing action. Thus, while the use of the aldehyde released during development is described herein primarily in terms of hardening action on gelatin, it will be recognized that other uses are envisioned.

This invention has been described in detail with particular reference to preferred embodiments thereof, but it will be understood that variations and modifications can be effected within the spirit and scope of the invention as described hereinabove and as defined in the appended claims.

I claim:

1. A method of forming a relief image comprising (a) developing an exposed unhardened silver halide emulsion of a photographic element with a composition consisting essentially of a compound having the following formula:

in which R is hydrogen or a lower alkyl group, and R is an aryl group, thereby forming an image of hardened silver halide emulsion in the exposed areas;

(b) removing unexposed unhardened silver halide emulsion, thereby forming said relief image.

2. The method of claim 1 wherein R is phenyl and R is hydroxymethyl.

3. The method of claim 1 wherein R is phenyl and R is methyl.

4. The method of claim 2 wherein said compound is present in said composition in an amount ranging from about 0.2 to about 4 grams per liter.

5. The method of claim 3 wherein said compound is present in said composition in an amount ranging from about 0.2 to about 4 grams per liter.

6. The method of claim 4 wherein said composition also contains ascorbic acid as an auxiliary developing agent.

7. The method of claim 5 wherein said composition also contains ascorbic acid as an auxiliary developing agent.

8. A process comprising imagewise hardening and developing an exposed unhardened silver halide emulsion with a composition consisting essentially of compound having the following formula:

N l. in which R is hydrogen or a lower alkyl group, and R is an aryl group.

9. The process of claim 8 wherein R is phenyl and R is hydroxymethyl.

10. The process of claim 8 wherein R is phenyl and R is methyl.

11. The process of claim 9 wherein said compound is present in said composition in an amount ranging from about 0.2 to about 4 grams per liter.

12. The process of claim 10 wherein said compound is present in said composition in an amount ranging from about 0.2 to about 4 grams per liter.

13. The process of claim 11 wherein said composition also contains ascorbic acid as an auxiliary developing agent.

14. The process of claim 12 wherein said composition also contains ascorbic acid as an auxiliary developing agent.

References Cited UNITED STATES PATENTS 2,289,367 7/1942 Kendall 96-66 2,772,282 11/1956 Allen et al. 96-66 3,041,170 6/1962 Haist et al. 96-66 3,192,046 6/1965 Kennard et al 96-66 3,221,023 11/1965 De Marle et al. 96-66 3,380,829 4/1968 Mason et al. 96-111 X FOREIGN PATENTS 1,311,068 1/ 1962 France.

NORMAN G. TORCHIN, Primary Examiner.

R. E. MARTIN, Assistant Examiner.

U.S. C1. X.R. 96-66, 111 

